Legend
Insulation zone
Air tightness barrier
(note: this can also
act as a vapour
control layer)
Blue text
Guidance on thermal
continuity
Red text
Guidance on air
tightness
Rigid insulation /
plasterboard composite
Values used in psi calculations
Material
-values used
in calculations
(W/mK)
Plasterboard
Insulation (generic)
Plywood sheathing
Brick outer leaf
Mineral wool insulation
Concrete block
(dense) protected
0.21
0.04
0.13
0.77
0.044
1.13
Concrete block
(lightweight, high strength)
0.19
Timber frame
Concrete floor beam
Concrete screed
Render (cement/sand)
Gypsum plaster
(1000kg/m3)
0.13
2.3
1.15
1.0
0.4
Concrete roof tiles
EPDM membrane
Timber battens
Timber flooring
Chipboard
Floor joists
Aluminium
Steel
Stainless steel
Glass
Sarking felt
Insulation board
1.5
0.25
0.13
0.13
0.13
0.13
160
50
17
1
0.23
0.022
Timber batten /
service void (option)
Vapour control layer
Structural timber frame
General guidance notes
Alternative constructions
Insulation
Sheathing board
Breather membrane
Wall ties
Cavity
1. The rigid insulation / plasterboard
construction can be replaced other
finishes but this will require that thicker
insulation is used in the wall. Ensure
that the thermal conductivity of this
insulation is equal or less than that
used in the cavity of the timber frame,
to prevent interstitial condensation
problems.
2. Different constructions can be used to
provide an outer leaf but check that
there is sufficient ventilation provision
to prevent moisture from being trapped
within the wall.
Sealing membrane junctions
Outer leaf (brick shown)
3. All membranes should be taped,
stapled or bedded in adhesive as
identified by manufacturer. Repair all
tears in membranes before
commencing next stage of work.
Psi-value calculations
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Isometric cut-away view
4. For details of all thermal conductivity
values of materials used in the
psi-value calculations, see Appendix B
of the Introduction.
Detail 3.00
Thermal continuity checklist
Air tightness checklist
Ventilation gap equivalent to 5mm
minimum continuous opening at ridge
is required where the roof pitch is
1. Ensure that insulation layers in roof are
fitted perpendicularly, to cover junctions
2. Ensure that roof insulation fully laps timber
frame insulation
3. Install cavity barrier at the top of the wall.
1. Check that any air tightness barrier used
in the wall overlaps and is robustly joined
to the barrier in the ceiling
more than 10m
Proprietary cross flow
ventilator to maintain
minimum 25mm air gap
Timber batten to provide
fixing for plasterboard sheet
Vapour control layer in
wall and ceiling
Ventilation gap equivalent to
10mm minimum continuous
opening is required where
or
ventilation gap equivalent to
25mm minimum continuous
opening is required where
Cavity barrier giving 30 minute
fire resistance - ensure cavity
barrier is not breeched by
inappropriate rigid sheathing
insulation material
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
Design advice
Minimising condensation risk
Insulation between the studs
must be tightly fitted leaving no
gaps
20x38mm timber battens /
services void (optional)
Composite rigid insulation /
plasterboard
1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used in
details:
Note: See detail numbers 3.02 and 3.21 for
other junctions using this roof construction
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0464W/mK Pitched Roof: Ventilated Roofspace - Eaves
Detail 3.01
Thermal continuity checklist
Air tightness checklist
1. Ensure that insulation layers in roof are
fitted perpendicularly, to cover junctions
2. Ensure that roof insulation butts against
the timber sheathing in the wall
3. Install cavity barrier at the top of the wall.
1. Check that any air tightness barrier used
in the wall overlaps and is robustly joined
to the barrier in the ceiling
Loft insulation continued up
to outer face of the rigid
sheathing
Full depth dwang required to
secure roof bracing at a level
above the rafter ties.
Alternative batten and bracing
details can also be used
Cavity barrier giving 30
minute fire resistance ensure cavity barrier is not
breeched by inappropriate
rigid sheathing insulation
material
Timber runner to provide fixing
for plasterboard sheet
Design advice
Minimising condensation risk
Cavity ventilator
Vapour control layer in
wall and ceiling
Insulation between the
studs must be tightly fitted
leaving no gaps
1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used in
details:
Note: See detail numbers 3.01 and 3.21 for
other junctions using this roof construction
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.1006W/mK Pitched Roof: Ventilated Roofspace - Gable
Detail 3.02
Thermal continuity checklist
Minimum 50mm ventilation path over insulation
1. Ensure that insulation is fitted tightly within
the timber frame
2. Ensure that insulation layers in roof are
fitted perpendicularly to cover junctions
3. Install cavity barrier at the top of the wall.
Air tightness checklist
1. Check that any air tightness barrier used
in the wall overlaps with the barrier in the
ceiling
Masonry built up
between ladder legs
Cavity ventilator
Design advice
Cavity barrier giving 30
minute fire resistance ensure cavity barrier is not
breeched by inappropriate
rigid sheathing insulation
material
Minimising condensation risk
Where two insulation types are
used together see
supplementary guidance
Timber runner to provide fixing
for plasterboard sheets
Note: this construction is
typically used where there
are habitable rooms within
the roof construction
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
Vapour control layer in
wall and ceiling
Insulation between the
studs must be tightly fitted
leaving no gaps
1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used in
details:
Note: See detail numbers 3.04, 3.05 and 3.22
for other junctions using this roof construction
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0472W/mK Pitched Roof: Ventilated Rafter Void - Gable
Detail 3.03
Thermal continuity checklist
1. Ensure that insulation layers in roof are
fitted perpendicularly, to cover junctions
2. Ensure that roof insulation overlaps with
the top of the timber frame wall, with
minimum 50mm overlap at the narrowest
point
3. Install cavity barrier at the top of the wall
Air tightness checklist
Ventilation gap equivalent to
5mm minimum continuous
opening is required at ridge
to batten space
1. Check that any air tightness barrier used
in the wall overlaps with the barrier in the
ceiling
Rigid insulation used as sarking.
Insulation to be vapour permeable
Vapour permeable membrane
(with a vapour resistance of
not more than 0.6MN.s/g)
Lap roof and wall insulation
minimum 150mm thickness at
narrowest point
Proprietary over
fascia ventilator
Ventilation to
batten void
Alternative position for
plasterboard ceiling
Timber batten to provide fixing
for plasterboard sheets
Vapour control layer in
wall and ceiling
Cavity barrier giving 30 minute
fire resistance - ensure cavity
barrier is not breeched by
inappropriate rigid sheathing
insulation material
Insulation between the
studs must be tightly
fitted leaving no gaps
Note: this construction is
typically used where there
are habitable rooms within
the roof construction
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
Design advice
Minimising condensation risk
1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used in
details:
Note: See detail numbers 3.03, 3.05 and 3.22
for other junctions using this roof construction
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0284W/mK Pitched Roof: Ventilated Batten Void (warm roof) - Eaves
Detail 3.04
Thermal continuity checklist
1. Ensure that insulation layers are fitted
perpendicularly, to cover junctions
2. Ensure that roof insulation fully laps timber
frame insulation
3. Install cavity barrier at the top of the wall.
Air tightness checklist
Note: this construction is
typically used where there
are habitable rooms within
the roof construction
1. Check that any air tightness barrier used
in the wall overlaps with the barrier in the
ceiling
Minimum 50mm ventilation path over insulation
Vapour
permeable
membrane
(with a vapour
resistance of
not more than
0.25 MN.s/g)
Design advice
Minimising condensation risk
Compressible filler
Cavity ventilator
Cavity barrier giving 30
minute fire resistance ensure cavity barrier is not
breeched by inappropriate
rigid sheathing insulation
material
Where two insulation types are
used together see
supplementary guidance
Timber runner to provide fixing
for plasterboard sheets
Vapour control layer in
wall and ceiling
Insulation between the studs must
be tightly fitted leaving no gaps
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used in
details:
Note: See detail numbers 3.03, 3.04 and 3.22
for other junctions using this roof construction
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0431W/mK Pitched Roof: Ventilated Batten Void (warm roof) - Gable
Detail 3.05
Thermal continuity checklist
1. Ensure that insulation layers in roof are
fitted perpendicularly, to cover junctions
2. Ensure that roof insulation fully laps timber
frame insulation
3. Install cavity barrier at the top of the wall.
Air tightness checklist
1. Check that any air tightness barrier used
in the wall overlaps with the barrier in the
ceiling
Vapour control layer turned up edge
of roof insulation, lapped with roof
waterproofing layer and sealed
Eaves - fix full height blocking
piece and tightly fit insulation into
void and under deck
Membrane roof construction
Verge - tightly fit insulation
into void over wall and
under deck (not shown)
Design advice
Vapour control layer in ceiling
Compressible filler
Cavity ventilator
Cavity barrier giving 30
minute fire resistance ensure cavity barrier is not
breeched by inappropriate
rigid sheathing insulation
material
Timber batten to be provided to
cover over junction between
plasterboard sheets
Vapour control layer in wall
Insulation between the
studs must be tightly fitted
leaving no gaps
Minimising condensation risk
1. Check ventilation paths are clear before
installing insulation above the ceiling
2. A vapour barrier is required at ceiling
level, to prevent moisture from entering
into the roof construction
3. The option shown here includes a vapour
control layer and insulation as part of a
membrane roof construction. Similar
details could be used for a profiled metal
decking roof but consult with
manufacturer regarding ventilation
requirements.
Thermal Resistance of insulation used in
details:
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0536W/mK Timber Flat Roof
Detail 3.06
Thermal continuity checklist
Air tightness checklist
1. Ensure that insulation layers in roof are
fitted perpendicularly, to cover junctions
2. Ensure that roof insulation butts against
the timber wall sheathing with a minimum
of 50mm overlap at narrowest point
3. Install cavity barrier at the top of the wall
1. Check that any air tightness barrier used
in the wall overlaps with the barrier in the
ceiling
Compressible filler
Roofing membrane to be taken minimum
150mm above finished roof level
Tightly fit compressible insulant between the wall
studs above the level of the roof deck
Vapour control layer turned up edge
of roof insulation, lapped with
breather membrane from cavity wall
Vapour control layer
Design advice
Minimising condensation risk
Cavity barrier
giving 30 minute
fire resistance ensure cavity
barrier is not
breeched by
inappropriate rigid
sheathing
insulation material
Vapour control layer in
wall and ceiling
Insulation between the studs must be
tightly fitted leaving no gaps
1. Check ventilation paths are clear before
installing insulation above the ceiling
2. A vapour barrier is required at ceiling
level, to prevent moisture from entering
into the roof construction
3. The option shown here includes a vapour
control layer and insulation as part of a
membrane roof construction. Similar
details could be used for a profiled metal
decking roof but consult with
manufacturer regarding ventilation
requirements.
Thermal Resistance of insulation used in
details:
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0299W/mK Timber Flat Roof with Parapet
Detail 3.07
Thermal continuity checklist
Air tightness checklist
1. Check that there is no debris in the cavity
2. Install cavity barrier around opening
1. Install window to overlap with outer leaf of
wall finish.
Alternative:
If window lines through with the bottom of
the opening in the external finish, some
means of preventing a direct line of air
infiltration will be required
2. Install air tightness seal between the
inside face of the window and the
structural finish of the window opening
Insulation between the
studs must be tightly
fitted leaving no gaps
Cavity tray with
minimum upstand
of 140mm and
stop ends
Use approved lintol
details from timber
frame supplier
30 minute fire
resisting
proprietary
insulating cavity
barrier with
integral DPC
Vapour control layer
Design advice
Minimising condensation risk
1. Alternative internal finish at window
reveal - use insulation backed
plasterboard
Compressible fill
Weep Hole
Thermal Resistance of insulation used in
details:
Sealant at window frame
If position of window head is
lower than or level with the
underside of the lintol, a larger
compressible filler will be
required to stop up a potential
air infiltration route
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
Psi value = 0.121W/mK
Insulate the window reveal
Air tightness tape
Sealant to back of frame
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Lintel at Window Head
Detail 3.08
Thermal continuity checklist
1. Check that there is no debris in the cavity
2. Install cavity barrier around opening
Air tightness checklist
1. Install window to overlap with outer leaf of
wall finish.
Alternative:
If window lines through with the bottom of
the opening in the external finish, some
means of preventing a direct line of air
infiltration will be required
2. Install air tightness seal between the
inside face of the window and the
structural finish of the window opening
30 minute fire resisting cavity
barrier with integral DPC
Sealant at window frame
Air tightness tape and
sealant to back of frame
Insulate the window reveal
Vapour control layer in wall
Jamb detail
Compressible
filler between
window and cill
Solid cill acts as cavity
closer. If pressed cill is
used, a 30 minute fire
rated thermally insulated
cavity closer will be
requied
Design advice
Air tightness tape and
sealant to back of frame
Insulate the window reveal
Minimising condensation risk
1. Alternative internal finish at window
reveal - use insulation backed
plasterboard
Thermal Resistance of insulation used in
details:
DPC lapped
behind cill and
below window
Vapour control
layer in wall
Insulation between the
studs must be tightly
fitted leaving no gaps
Cill detail
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
Psi value (jamb)=0.0328W/mK
Psi value (cill) = 0.0934W/mK
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Windows and Doors - Jambs and Cills
Detail 3.09
Thermal continuity checklist
Air tightness checklist
1. Use a lightweight loadbearing concrete
block where the wall abuts the concrete
slab to minimise thermal bridging
2. Use a perimeter strip of insulation where
the concrete slab abuts the concrete
blockwork wall
1. Ensure that any air tightness barrier used
in the wall overlaps onto the floor slab
Vapour control layer in wall
Seal between the wall and floor
membrane with a flexible sealant or
seal the gap between skirting board
and floor using a flexible sealant
Vapour control layer below
timber floor finish
External ground level
Design advice
Minimising condensation risk
Damp proof membrane
above or below slab
20mm strip of perimeter
insulation with thermal
conductivity ( value) not
exceeding 0.025 W/mK around
slab and any screed
1. Check that concrete slab is level and
clear of debris before fitting the insulation
at floor level
2. If a screed finish is used instead of a
timber floor, use a strip of perimeter
insulation with a minimum R value of
Alternative detail
3. Using lightweight blockwork (e.g. with
value of 0.19W/mK) to improve the
thermal performance at the junction where
the external wall and ground floor
constructions meet will change the psi
value
Thermal Resistance of insulation used in
details:
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.1145W/mK Ground Bearing Floor: Insulation Above Slab
Detail 3.10
Thermal continuity checklist
Air tightness checklist
1. Use a lightweight loadbearing concrete
block where the wall abuts the concrete
slab to minimise thermal bridging
2. Use a perimeter strip of insulation where
the concrete slab abuts the concrete
blockwork wall
Vapour control layer in wall
1. Check that any air tightness barrier used
in the wall overlaps onto the floor slab
Seal between the wall and floor
membrane with a flexible sealant or
seal the gap between skirting board
and floor using a flexible sealant
External ground level
Design advice
Minimising condensation risk
Damp proof membrane
50mm strip of perimeter
insulation with thermal
conductivity ( value) not
exceeding 0.025 W/mK around
slab and any screed
1. If a screed finish is used instead of a
timber floor, use a strip of perimeter
insulation with a minimum R value of
Alternative detail
2. Using lightweight blockwork (e.g. with
value of 0.19W/mK) to improve the
thermal performance at the junction
where the external wall and ground floor
constructions meet will change the psi
value
Thermal Resistance of insulation used in
details:
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.1733W/mK Ground Bearing Floor: Insulation Below Slab
Detail 3.11
Thermal continuity checklist
Air tightness checklist
Vapour control layer in wall
1. Ensure that floor insulation butts against
the insulation in the external wall
Add timber batten to cover the floor/wall junction. Use
air tightness tape at junction of air barrier in wall and
floor. Seal between the wall and floor membrane with a
flexible sealant or seal the gap between skirting board
and floor using a flexible sealant
1. Check that any air tightness barrier used
in the wall overlaps with the barrier in the
floor
Air tightness barrier below
timber floor finish
Insulation directly under flooring
supported on netting draped over
joists and stapled at required depths
External ground level
Solum
Damp proof membrane
Design advice
Minimising condensation risk
1. Check that all ventilation paths are clear
before installing the floor insulation
Sub floor ventilation should be
per run of external wall or
Alternative detail
2. Using lightweight blockwork (e.g.
with value of 0.19W/mK) to improve
thermal performance at the junction
where the external wall and ground floor
constructions meet will change the psi
value
3. If there are concerns about damaging the
air tightness membrane in the floor finish
during construction, an additional services
void can be created using timber battens
on top of the floor joists
Thermal Resistance of insulation used in
details:
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0423W/mK Timber Suspended Ground Floor
Detail 3.12
Thermal continuity checklist
Air tightness checklist
Cavity barriers giving 30 minute
fire resistance - ensure cavity
barriers are not breeched by
inappropriate insulation material
in the timber frame
1. Check that there is no debris in the cavity
2. Install cavity barrier at junction of wall
1. Check that any air tightness barrier used
in the internal wall overlaps with the
barrier in the external wall
Vapour control layer in wall
Design advice
Minimising condensation risk
1. Check that insulation is fitted between
timber studs at corner junctions
Thermal Resistance of insulation used in
details:
For more information on
acoustic details see
guidance in Section 5 of
the Technical Standards
Plan view
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0725W/mK Separating Wall
Detail 3.13
Thermal continuity checklist
Air tightness checklist
1. Check that there is no debris in the cavity
2. Install cavity barrier in line with floor
construction
1. Check that any air tightness barrier used
in the external wall overlaps with the
barrier in the floor
Vapour control layer in wall
Seal between the wall and floor
membrane with a flexible sealant or seal
the gap between skirting board and floor
using a flexible sealant
Cavity
ventilator
Cavity barrier
giving 30 minute
fire resistance ensure cavity
barrier is not
breeched by
inappropriate rigid
sheathing
insulation material
Design advice
Vapour control layer in wall
Insulation between the studs must be
tightly fitted leaving no gaps
Minimising condensation risk
1. Check that insulation is tightly fixed to the
timber studs adjacent to the floor junction,
leaving no gaps
Thermal Resistance of insulation used in
details:
Separating floors to comply with
Section 2: Fire and Section 5:
Noise
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0353W/mK Timber Separating Floor
Detail 3.14
Thermal continuity checklist
Air tightness checklist
1. Check that there is no debris in the cavity
2. Install cavity barrier as necessary
1. Check that any air tightness barrier used
in the external wall overlaps with the
barrier in the floor
Vapour control layer in wall
Seal between the wall and floor
membrane with a flexible sealant or
seal the gap between skirting board
and floor using a flexible sealant
Install air tightness barrier around
joists, then lap membrane from
walls over it and tape junction
Design advice
Vapour control layer in wall
Insulation between the
studs must be tightly
fitted, leaving no gaps
Minimising condensation risk
1. Check that insulation is tightly fixed to the
timber studs adjacent to the floor junction,
leaving no gaps
Thermal Resistance of insulation used in
details:
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0574W/mK Intermediate Floor / External Wall
Detail 3.15
Thermal continuity checklist
Air tightness checklist
Vapour contol layer in wall
1. Ensure that insulation is tightly fitted
between the timber floor joists
2. Install cavity barrier as necessary
Use air tightness tape at junction of air barrier in wall
and floor. Seal between the wall and floor membrane
with a flexible sealant or seal the gap between skirting
board and floor using a flexible sealant
Air tightness barrier below
timber floor finish
1. Check that any air tightness barrier used
in the internal wall overlaps with the
barrier in the floor
Insulation directly under flooring supported on netting draped over
joists and stapled at required depths
Damp proof membrane
Solum
Design advice
Minimising condensation risk
Sub floor ventilation should be
per run of external wall or
1. Check that all ventilation paths are clear
before installing the floor insulation
Alternative Detail
2. Lightweight thermal blockwork can be
used in the separating wall to improve the
thermal performance but this will also
reduce the acoustic performance of the
wall. If this alternative is used then
additional elements will be required to
meet Section 5 of the Technical
Standards.
Thermal Resistance of insulation used in
details:
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0713W/mK Ground Floor/Separating Wall Junction- timber suspended floor Detail 3.16
Thermal continuity checklist
1. Ensure that insulation is tightly fitted
against the separating floor
Air tightness checklist
Vapour control layer in wall
1. Check that any air tightness barrier used
in the internal wall overlaps onto the floor
slab
Seal between the wall and floor
membrane with a flexible sealant or
seal the gap between skirting board
and floor using a flexible sealant
Design advice
Minimising condensation risk
1. If a screed finish is used instead of a
timber floor, use a strip of perimeter
insulation with a minimum R value of
Damp proof membrane
Lightweight loadbearing concrete
blockwork to minimise thermal bridging
Alternative Detail
2. Heavyweight thermal blockwork can be
used in the separating wall below slab
level but this will reduce the thermal
performance of this junction. Additional
construction elements may be required
along with lightweight blockwork in order
to meet the acoustic requirements of
Section 5 of the the Technical Standards
Thermal Resistance of insulation used in
details:
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.2765W/mK Concrete Ground Floor/ Separating Wall: Insulation Below Slab Detail 3.17
Thermal continuity checklist
Air tightness checklist
1. Ensure that insulation is tightly fitted
against the separating floor
1. Check that any air tightness barrier used
in the internal wall overlaps onto the floor
slab
Vapour control layer in wall
Seal between the wall and floor
membrane with a flexible sealant or
seal the gap between skirting board
and floor using a flexible sealant
Seal air tightness
membrane to floor slab
Vapour barrier in floor
Design advice
Minimising condensation risk
Damp proof membrane
1. Check that concrete slab is level and
clear of debris before fitting the insulation
at floor level
2. If a screed finish is used instead of a
timber floor, use a strip of perimeter
insulation with a minimum R value of
Alternative Detail
3. Lightweight thermal blockwork can be
used in the separating wall to improve the
thermal performance but this will also
reduce the acoustic performance of the
wall. If this alternative is used then
additional elements will be required to
meet Section 5 of the Technical
Standards.
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Thermal Resistance of insulation used in
details:
Timber Frame
Psi value = 0.0146W/mK Concrete Ground Floor/ Separating Wall: Insulation Above Slab Detail 3.18
Thermal continuity checklist
Air tightness checklist
1. Ensure that insulation is tightly fitted
1. Check that any air tightness barrier
used in the internal wall overlaps with
the barrier in the floor
Alternative:
Ensure that a continuous air tightness
barrier from the wall wraps around the
end of the floor construction, leaving
no gaps
Vapour control layer in wall
Seal between the wall and floor
membrane with a flexible sealant or
seal the gap between skirting board
and floor using a flexible sealant
Vapour control layer below
timber floor finish
Cavity barrier
Design advice
Vapour control layer in ceiling
Minimising condensation risk
See general guidance notes
Vapour control layer in wall
Thermal Resistance of insulation used in
details:
Insulation between the studs
must be tightly fitted
Separating floors require
additional layers and components
to comply with Section 2: Fire
and Section 5: Noise
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0241W/mK Separating Floor / Wall Junction
Detail 3.19
Thermal continuity checklist
Air tightness checklist
1. Ensure that insulation is tightly fitted
1. Check that any air tightness barrier
used in the internal wall overlaps with
the barrier in the floor
Alternative:
Ensure that a continuous air tightness
barrier from the wall wraps around the
end of the floor construction, leaving
no gaps
Vapour control layer in wall
Seal between the wall and floor
membrane with a flexible sealant or
seal the gap between skirting board
and floor using a flexible sealant
Cavity barrier
Design advice
Install air tightness barrier around
joists, then lap membrane from
walls over it and tape junction
Vapour control layer in wall
Insulation between the studs
must be tightly fitted
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
Minimising condensation risk s
See general guidance notes
Thermal Resistance of insulation used in
details:
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0333W/mK Intermediate Floor
Detail 3.20
Thermal continuity checklist
Air tightness checklist
1. Install a cavity barrier at the top of the wall
2. Ensure that insulation layers in the roof are
fitted perpendicularly, to cover junctions
1. Check that there are no gaps
between the top of the masonry and
the underside of the roof
2. Check that the air tightness barrier in
the wall overlaps with the barrier in
the ceiling
Cavity barrier giving 30
minute fire resistance ensure cavity barrier is not
breeched by inappropriate
rigid sheathing insulation
material
Where two insulation types
are used together see
supplementary guidance
Design advice
Minimising condensation risk
1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used in
details:
Cavity barrier is used in line with
ceiling insulation to prevent thermal
bypass.Use dense insulation or
proprietary cavity barrier in sleeve
Separating walls require
additional layers and components
to comply with Section 2: Fire
and Section 5: Noise
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
Vapour control layer in
wall and ceiling
Note: See detail numbers 3.01 and 3.02 for
other junctions using this roof construction
Insulation between the studs
must be tightly fitted
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0132W/mK Pitched Roof: Cold Roof / Separating Wall junction
Detail 3.21
Thermal continuity checklist
Air tightness checklist
Minimum 50mm ventilation path over insulation
1. Install a cavity barrier at the top of the wall
2. Ensure that insulation layers in the roof are
fitted perpendicularly, to cover junctions
Cavity barrier giving 30
minute fire resistance ensure cavity barrier is not
breeched by inappropriate
rigid sheathing insulation
material
1. Check that there are no gaps
between the top of the masonry and
the underside of the roof
2. Check that the air tightness barrier in
the wall overlaps with the barrier in
the ceiling
Where two insulation types
are used together see
supplementary guidance
Vapour control layer
in wall and ceiling
Insulation between the studs
must be tightly fitted
Design advice
Minimising condensation risk
1. Check ventilation paths are clear before
installing insulation above the ceiling
Thermal Resistance of insulation used in
details:
Separating walls require
additional layers and components
to comply with Section 2: Fire
and Section 5: Noise
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
Note: this construction is
typically used where there
are habitable rooms within
the roof construction
Note: See detail numbers 3.03, 3.04 and 3.05
for other junctions using this roof construction
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0481W/mK Pitched Roof: Ventilated Batten Void / Separating Wall Junction Detail 3.22
Thermal continuity checklist
Air tightness checklist
1. Check that there is no debris in the cavity
2. Install cavity barrier
1. Ensure that any air tightness barrier used
in the external wall overlaps at the corner
Cavity barrier giving 30 minute
fire resistance - ensure cavity
barrier is not breeched by
inappropriate insulation
material
Insulation between
the studs must be
tightly fitted leaving
no gaps
Design advice
Minimising condensation risk
Vapour control
layer
1. Check that insulation is tightly fixed to
the timber studs at the corner junction,
leaving no gaps
Thermal Resistance of insulation used in
details:
Plan view
HEAT 2.7 software image of isotherms
through junction detail.
For illustrative purposes only.
This example should be read in conjunction with the guidance in the introduction to this document. It illustrates the reduction
of unwanted infiltration in buildings and provides a Psi value for this junction situation which can be used in calculation
provided the principles outlined and any identified component specification are followed.
Timber Frame
Psi value = 0.0179W/mK Wall Junction
Detail 3.23